Not Losing Weight? The Answer May Be in Your Poop

Leah Groth
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updated on September 25, 2018

About the Author:

Leah Groth

Leah Groth is a writer and editor currently based in Philadelphia. She has covered topics such as entertainment, parenting, health & wellness for xoJane, Babble, Radar, Fit Pregnancy, Mommy Nearest, Living Healthy and PopDust.

According to a study published this month in the International Journal of Obesity, weight loss may be dependent on the specific type of bacteria that breeds in your gut and (sorry) is present in your poop.

Researchers in Denmark followed 62 overweight participants who maintained one of two diets for 25 weeks — the high-fiber New Nordic Diet (think dark greens, berries and whole grains) and the grainless standard Danish diet (lean meat, eggs, lettuce and coffee) — measuring the ratio of two types of gut bacteria called Prevotella and Bacteroides in their poop. And the results were quite interesting: Those on the New Nordic Diet lost weight — about seven pounds more than the standard Danish diet — only if they had a high ratio of Prevotella to Bacteroides in their feces. For those with a low ratio, it didn’t really matter which diet they followed because there wasn’t a big difference in terms of weight loss.

In other words, people with different amounts of gut bacteria responded differently to the same diet — which may totally explain why your best friend’s “miracle” diet resulted in a weight loss of zero pounds for you.

“These results are a breakthrough demonstrating that certain bacterial species play a decisive role in weight regulation and weight loss,” said lead researcher Arne Astrup. “Now we can explain why a high-fiber diet does not always lead to weight loss. Human intestinal bacteria is an important part of the answer and will from now on play a role in the treatment of the overweight.”

This latest research is a reminder that, for many people, weight loss may be more than just cutting calories and increased exercise: There is no “one size fits all” approach to dieting. It's also important to remember that your gut bacteria ratio is something that can be changed. Always consult a doctor before making any changes to your diet, but if you have concerns it can’t hurt to ask about probiotics or at-home services like Viome, which can test your feces and offer suggestions to improve your gut health.